Curing method and apparatus

ABSTRACT

The present invention provides a method for curing a light curable sealant in an article. The article includes opposing first and second substrates. The light curable sealant is used to attach the first substrate to the second substrate. The method includes irradiating steps (a) and (b). In the step (a), the article is irradiated by a light entering the article from the first substrate to reach the light curable sealant. In the step (b), the article is irradiated by a light entering the article from the second substrate to reach the light curable sealant. The present invention further provides curing apparatuses for accomplishing the aforementioned method.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method and an apparatus for curing alight curable sealant, and more particularly to a curing method and anapparatus used in a liquid crystal display manufacturing process.

2. Description of the Related Art

An liquid crystal display cell typically includes two oppositelypositioned first and second substrates and a liquid crystal layerinterposed therebetween. The two substrates are typically affixed toeach other with a thermosetting epoxy. However, this method needs arelatively high curing temperature which the liquid crystal materialcannot bear, and therefore the step of curing the thermosetting epoxyshould be conducted prior to filling of the liquid crystal material.

U.S. Pat. No. 5,263,888 discloses a one drop fill (ODF) method includingthe steps of applying an adhesive onto the entire periphery of the firstsubstrate, dropping the liquid crystal material to the first substrate,superposing the second substrate upon the first substrate and pressingthe substrates until a gap between the substrates reaches apredetermined value (typically 3-10 micrometers), and curing theadhesive. In the step of pressing the substrates, the liquid crystalmaterial spreads to fill the space between the substrates therebyforming the liquid crystal layer. This method significantly reduces thenumber of the manufacturing steps and increases the manufacturingefficiency. However, instead of using the thermosetting epoxy, the onedrop fill method must use a UV curable sealant which cures at near roomtemperature.

For simplifying the manufacturing process and increasing themanufacturing efficiency, the UV curing step is conducted by irradiatingthe liquid crystal display cell with the UV radiation entering theliquid crystal display cell only from the first substrate or the secondsubstrate. Therefore, the UV radiation can't reach and cure the sealantunless it penetrates the first substrate or the second substrate first.However, each pixel on the first substrate is typically surrounded by ablack matrix, and the second substrate is typically provided with ametallization pattern. Therefore, there is a problem of accessingregions of sealant with the UV radiation when there are black matrix ormetallization pattern through which the UV cannot penetrate therebyresulting in incomplete curing of the sealant. There is mountingevidence that uncured sealant will react with the liquid crystal therebycausing the latter to degrade in its performance as a liquid crystalmaterial.

Furthermore, if the UV radiation enters the liquid crystal display cellonly from the first substrate, the black matrix that blocks the sealantfrom light must be kept away from the sealant in order to ensure thatthe UV curable sealant can be cured completely. But this means the areaoutside the display region of liquid crystal panel will be increased orthe area of the display region will be decreased if the area of theliquid crystal panel remains the same, either the former design or thelatter design varies from the developing trend of the liquid crystaldisplay device.

SUMMARY OF THE INVENTION

Therefore, it is an object of the invention to provide an improvedmethod and apparatus for curing a light curable sealant designed foraffixing two substrates that can significantly suppress occurrence ofincomplete curing of the sealant due to shadowing by the black matrix orthe metallization pattern. The curing method and apparatus are intendedto be used with the “one drop fill” method since it is becoming thepreferred manufacturing method of the liquid crystal display device.

The liquid crystal display cell generally includes opposing firstsubstrate and second substrate and a light curable sealant (e.g., a UVcurable sealant) for attaching the first substrate to the secondsubstrate. A liquid crystal layer is sandwiched between the first andthe second substrates. Generally, the first substrate is provided with alight-shielding matrix formed thereon and the second substrate isprovided with a metallization pattern formed thereon.

To achieve the above listed and other objects, the present inventionprovides a curing method including the following steps: (a) irradiatingthe liquid crystal display cell with light entering the liquid crystaldisplay cell from the first substrate to reach the light curable sealantthereby avoiding the metallization pattern on the second substrate fromblocking the irradiating step (a); and (b) irradiating the liquidcrystal display cell with light entering the liquid crystal display cellfrom the second substrate to reach the light curable sealant therebyavoiding the light-shielding matrix on the first substrate from blockingthe irradiating step (b). To simplify the manufacturing process andincrease the manufacturing efficiency, the steps of (a) and (b) arepreferably conducted simultaneously. Since the curing method of thepresent invention is conducted by irradiating the liquid crystal displaycell with light entering from the first substrate and the secondsubstrate, occurrence of incomplete curing of the sealant due toshadowing by the black matrix or the metallization pattern issignificantly suppressed.

The present invention further provides curing apparatuses foraccomplishing the aforementioned method.

According to one embodiment of the present invention, the curingapparatus mainly includes first and second stages for holding a workpiece (e.g., the aforementioned liquid crystal display cell), a lightsource and means for transporting the work piece from the first stage tothe second stage.

According to another embodiment of the present invention, the curingapparatus mainly includes first and second stages, a light source,mechanism for holding and turning over the work piece and first andsecond transporting means. The first transporting means is configuredfor transporting the work piece from the first stage to the holding andturning over mechanism. The second means is configured for transportingthe work piece from the holding and turning over mechanism to the secondstage.

In the aforementioned embodiments, when the work piece is placed on thefirst stage, light generated by the light source enters the work piecefrom the first substrate to reach the light curable sealant; when thework piece is placed on the second stage, light generated by the lightsource enters the work piece from the second substrate to reach thelight curable sealant thereby the light curable sealant can be cured bylight entering the work piece from the first substrate and the secondsubstrate. Moreover, the aforementioned transporting means preferablyincludes a robot utilizing a chuck assembly to hold the work piece.

According to still another embodiment of the present invention, thecuring apparatus mainly includes means for supporting a work piece and alight source. The light source includes a first irradiation unit and asecond irradiation unit arranged on an opposite side of the work piecefrom the first irradiation unit. When the work piece is supported by thesupporting means, the light generated by the first irradiation unitenters the work piece from the first substrate to reach the lightcurable sealant, and the light generated by the second irradiation unitenters the work piece from the second substrate to reach the lightcurable sealant. In this embodiment, the work piece supporting means maybe a stage including a transparent work area for holding the work piecesuch that the light curable sealant is substantially not shadowed by thework piece supporting means thereby the light curable sealant can becured by light entering the work piece from the first substrate and thesecond substrate. Moreover, the work piece may include clamps forholding the edges of the first and second substrates, or include aplurality of pins for supporting the work piece.

According to still another embodiment of the present invention, there isprovided a liquid crystal display cell comprising a first substrate witha light-shielding matrix formed thereon, a second substrate with ametallization pattern formed thereon, a liquid crystal layer sandwichedbetween the first and the second substrates, and a light curable sealantfor attaching the first substrate to the second substrate, wherein thelight curable sealant is cured by (a) irradiating the liquid crystaldisplay cell with light entering the liquid crystal display cell fromthe first substrate to reach the light curable sealant; and (b)irradiating the liquid crystal display cell with light entering theliquid crystal display cell from the second substrate to reach the lightcurable sealant, whereby the light curable sealant is cured by the lightentering the liquid crystal display cell from the first and secondsubstrates.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects, advantages, and novel features of the invention willbecome more apparent from the following detailed description when takenin conjunction with the accompanying drawings.

FIG. 1 is a cross-sectional view of a portion of a liquid crystaldisplay device suitable for use in the present invention;

FIG. 2 is a cross-sectional view of a portion of a liquid crystaldisplay cell suitable for use in the present invention;

FIG. 3 a is a cross-sectional view of a curing apparatus according toone embodiment of the present invention;

FIG. 3 b is a cross-sectional view of a curing apparatus according toanother embodiment of the present invention;

FIG. 4 is a top plan view of a curing apparatus according to anotherembodiment of the present invention;

FIG. 5 is a cross-sectional view of a curing apparatus according toanother embodiment of the present invention;

FIG. 6 is a cross-sectional view of a curing apparatus according toanother embodiment of the present invention; and

FIG. 7 is a cross-sectional view of a curing apparatus according toanother embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention provides an improved method and apparatus forcuring a light curable sealant designed for affixing two substratestogether. The curing method and apparatus of the present invention areintended to be used with the “one drop fill” method since it is becomingthe preferred manufacturing method of the liquid crystal display device.

FIG. 1 shows a liquid crystal display device 110 mainly including aliquid crystal layer sealed in a liquid crystal display cell 120. Theliquid crystal display cell 120 includes a first substrate 130 and asecond substrate 140. The first substrate 130 is typically provided witha light-shielding matrix (e.g. black matrix 132), color filters 134 fordisplay color and a transparent electrode (e.g. ITO electrode) servingas a common electrode 136. The second substrate 130 is mainly providedwith a metallization pattern 142 (e.g. a plurality of gate lines anddata lines) formed thereon. It is preferred that the liquid crystaldisplay device used in the present invention is a thin film transistorliquid crystal display. Generally, the first substrate 130 is referredto as a color filter substrate because it is provided with colorfilters, and the second substrate 140 is referred to as a thin filmtransistor substrate.

As shown in FIG. 2, the first substrates 130 and the second substrate140 are affixed to each other by a light curable sealant 150. The UVcurable sealant 150 is typically positioned near a peripheral edge oftwo substrates 130 and 140 which are substantially transparent to lightexcept the regions of black matrix 132 and metallization pattern 142that prevent light from penetrating to reach the sealant 150.

Therefore, the present invention provides a curing method including twoirradiating steps (a) and (b). In the irradiating step (a), theirradiating light enters the liquid crystal display cell 120 from thefirst substrate 130 to reach the light curable sealant 150 whereby themetallization pattern 142 on the second substrate 140 will not block theirradiating step (a). In the irradiating step (b), the irradiating lightenters the liquid crystal display cell 120 from the second substrate 140to reach the light curable sealant 150 whereby the black matrix 132 onthe first substrate 130 will not block the irradiating step (b). Tosimplify the manufacturing process and increase the manufacturingefficiency, the steps of (a) and (b) are preferably conductedsimultaneously. Additionally, the light curable sealant may be a UVcurable sealant, and the light is irradiated from a UV irradiation unit.

Since the curing method of the present invention is conducted byirradiating the liquid crystal display cell with light entering from thefirst substrate 130 and the second substrate 140, occurrence ofincomplete curing of sealant due to shadowing of the black matrix 132and metallization pattern 142 is significantly suppressed.

FIGS. 3-7 illustrate the curing apparatuses according to preferredembodiments of the present invention and similar components have beengiven the same reference numerals.

FIG. 3 a illustrates a curing apparatus 200 according to one embodimentof the present invention. The curing apparatus mainly includes stages210, 220, an irradiation unit 230 and transporting means. It ispreferred that the stages 210, 220 can hold the work piece that is to beirradiated (e.g. the aforementioned liquid crystal display cell 120) andpermits movement and alignment of the liquid crystal display cell 120 inX and Y directions (horizontally) and ration in X-Y plane. A vacuumdevice such as a vacuum pump may be connected to the stages 210, 220thereby drawing a vacuum on the stages 210, 220 to secure the liquidcrystal display cell 120 thereon. If the sealant that is to be cured isa UV curable sealant, the irradiating units 230, 240 may be respectivelyprovided with a plurality of UV lights.

The transporting means of the present invention can engage the workpiece to retain or alter position of the work piece. The embodimentshown in FIG. 3 a includes a robot 250 with a chuck assembly 252. Thechuck assembly 252 preferably includes means for engaging and retainingthe work piece. The chuck assembly 252 may include a vacuum device suchas a vacuum pump for drawing a vacuum on the chuck assembly 252 tosecure the liquid crystal display cell 120 thereon. However, the presentinvention may include other devices such as clamps for holding theliquid crystal display cell 120.

The liquid crystal display cell 120 is placed on the stage 210 with thefirst substrate 130 thereof facing the irradiation unit 230. Therefore,the light from the irradiation unit 230 enters the liquid crystaldisplay cell 120 from the first substrate 130 to reach the light curablesealant. In the curing apparatus 200 shown in FIG. 3 a, the irradiationunit 240 is arranged on an opposite side of the stages 210, 220 from theirradiation unit 230. Therefore, the robot 250 must be designed to beable to suck the liquid crystal display cell 120 by the chuck assembly252 thereof and then place the liquid crystal display cell 120 on thestage 220 with its second substrate 140 facing the irradiation unit 240.Next, the light from the irradiation unit 240 enters the liquid crystaldisplay cell 120 from the second substrate 140 to reach the lightcurable sealant.

FIG. 3 b illustrates a curing apparatus 260 according to anotherembodiment of the present invention. The curing apparatus 260 ischaracterized in that the irradiation unit 240 is arranged on the sameside of the stages 210, 220 as the irradiation unit 230. Therefore, therobot 262 must be designed to be able to suck the liquid crystal displaycell 120 by the chuck assembly 252 thereof and then place the liquidcrystal display cell 120 on the stage 220 with its second substrate 140facing the irradiation unit 240.

FIG. 4 illustrates a curing apparatus 300 according to anotherembodiment of the present invention. The curing apparatus 300 mainlyincludes stages 210, 220, 210 a, 220 a, a plurality of irradiation units(not shown), mechanism 310 for holding and turning the work piece andtransporting means such as robots 250 a, 250 b, 250 c, 250 d. Themechanism 310 is preferably provided with a stage 312 including a vacuumdevice such as a vacuum pump for drawing a vacuum on the stage 312 tosecure the liquid crystal display cell 120 thereon.

Referring to FIG. 4, two liquid crystal display cells 120 are placed onthe stages 210, 210 a respectively. Since the irradiation units (notshown) are arranged above the supporting surface of the stages 210, 220,210 a, 220 a, the light from the irradiation unit enters the liquidcrystal display cell 120 from the first substrate 130 to reach the lightcurable sealant. Next, the two liquid crystal display cells 120 arerespectively placed on the stage 312 of the mechanism 310 by the robots250 a, 250 c. After a turning operation of the stage 312 is conducted,the two liquid crystal display cells 120 are respectively placed on thestages 220, 220 a by the robots 250 b, 250 d. At this time, the firstsubstrate 130 of the liquid crystal display device 120 faces the stages220, 220 a. Therefore, the light from the irradiation unit enters theliquid crystal display cell 120 from the second substrate 140 to reachthe light curable sealant. It should be understood that the robots 250a, 250 c or the robots 250 b, 250 d can be integrated into one device bybeing connected together.

FIG. 5 illustrates a curing apparatus 400 according to anotherembodiment of the present invention. The curing apparatus 400 mainlyincludes means for supporting a liquid crystal display cell 120 andirradiation units 230, 240. The irradiation unit 230 is arranged on anopposite side of the liquid crystal display cell 120 from theirradiation unit 240. In the curing apparatus 400 shown in FIG. 5, thework piece supporting means may be a stage 410 having a transparent workarea for holding the liquid crystal display cell 120 such that the lightcurable sealant is not shadowed by the stage 410. The stage 410 ispreferably made of transparent quartz material. Therefore, the lightgenerated by the irradiation unit 230 enters the liquid crystal displaycell 120 from the first substrate 130 to reach the light curablesealant, and the light generated by the irradiation unit 240 enters thework piece from the second substrate 140 to reach the light curablesealant.

FIG. 6 illustrates a curing apparatus 500 according to anotherembodiment of the present invention. The curing apparatus 500 issubstantially identical to the curing apparatus 400 shown in FIG. 5 withan exception that the work piece supporting means is a clamp 510. Theclamp 510 is configured for holding the edges of the first substrate 130and second substrate 140 of the liquid crystal display cell 120 suchthat light curable sealant won't be shadowed by the clamp 510.

FIG. 7 illustrates a curing apparatus 600 according to anotherembodiment of the present invention. The curing apparatus 600 issubstantially identical to the curing apparatus 400 shown in FIG. 5 withan exception that the work piece supporting means includes a pluralityof pins 610 for supporting the work piece.

Although the invention has been explained in relation to its preferredembodiment, it is to be understood that many other possiblemodifications and variations can be made without departing from thespirit and scope of the invention as hereinafter claimed.

1-4. (canceled)
 5. A curing apparatus, comprising: first and secondstages each having a surface adapted for holding a work piece havingopposing first and second substrates and a light curable sealant forattaching the first substrate to the second substrate; means fortransporting the work piece from the first stage to the second stage;and a light source, wherein, when the work piece is placed on the firststage, the light generated by the light source enters the work piecefrom the first substrate to reach the light curable sealant; and, whenthe work piece is placed on the second stage, the light from the lightsource enters the work piece from the second substrate to reach thelight curable sealant, whereby the light curable sealant is cured by thelight entering the work piece from the first and second substrates. 6.The curing apparatus as claimed in claim 5, wherein the light sourcecomprises a first irradiation unit and a second irradiation unitarranged on an opposite side of the first and second stages from thefirst irradiation unit.
 7. The curing apparatus as claimed in claim 5,where the transporting means comprises a robot utilizing a chuckassembly to hold the work piece.
 8. A curing apparatus, comprising:first and second stages each having a surface adapted for holding a workpiece having opposing first and second substrates and a light curablesealant for attaching the first substrate to the second substrate;mechanism for holding and turning over the work piece; and a lightsource, wherein, when the work piece is placed on the first stage, thelight generated by the light source enters the work piece from the firstsubstrate to reach the light curable sealant; and, when the work pieceis placed on the second stage, the light from the light source entersthe work piece from the second substrate to reach the light curablesealant, whereby the light curable sealant is cured by the lightentering the work piece from the first and second substrates.
 9. Thecuring apparatus as claimed in claim 8, wherein the light sourcecomprises a first irradiation unit facing the surface of the firststage, and a second irradiation unit facing the surface of the secondstage.
 10. The curing apparatus as claimed in claim 8, furthercomprising: first means for transporting the work piece from the firststage to the holding and turning over mechanism; and second means fortransporting the work piece from the holding arid turning over mechanismto the second stage.
 11. The curing apparatus as claimed in claim 10,wherein the transporting means comprises a robot utilizing a chuckassembly to hold the work piece.
 12. A curing apparatus, comprising:means for supporting a work piece having opposing first and secondsubstrates and a light curable sealant for attaching the first substrateto the second substrate; and a light source including a firstirradiation unit and a second irradiation unit arranged on an oppositeside of the work piece from the first irradiation unit, wherein, whenthe work piece is supported by the supporting means, the light generatedby the first irradiation unit enters the work piece from the firstsubstrate to reach the light curable sealant, and the light generated bythe second irradiation unit enters the work piece from the secondsubstrate to reach the light curable sealant.
 13. The curing apparatusas claimed in claim 12, wherein the supporting means comprises a stageincluding a transparent work area for holding the work piece.
 14. Thecuring apparatus as claimed in claim 12, wherein the supporting meanscomprises clamps for holding the edges of the first and secondsubstrates of the work piece.
 15. The curing apparatus as claimed inclaim 12, wherein the supporting means comprises a plurality of pins forsupporting the work piece.
 16. The curing apparatus as claimed in claim12, wherein the light curable sealant is substantially not shadowed bythe supporting means thereby the light curable sealant is cured by thelight entering the work piece from the first and second substrates.17-19. (canceled)